One common method for printing images on a receiver member is referred to as electrography. In a particular implementation of this method, known as electrophotography, an electrostatic image is formed on a dielectric member by uniformly charging the dielectric member and then discharging selected areas of the uniform charge to yield an image-wise electrostatic charge pattern. Such discharge is typically accomplished by exposing the uniformly charged dielectric member to actinic radiation provided by selectively activating particular light sources in an LED array or a laser device directed at the dielectric member. After the image-wise charge pattern is formed, the pigmented (or in some instances, non-pigmented) toner particles are given a charge, substantially opposite the charge pattern on the dielectric member and brought into the vicinity of the dielectric member so as to be attracted to the image-wise charge pattern to develop such pattern into a visible image.
Thereafter, a suitable receiver member, sometimes simply referred to as a receiver, (e.g., a cut sheet of plain bond paper) or an intermediate transfer member, sometimes simply referred to as an intermediate, (e.g. a compliant or non-compliant roller or web) is brought into juxtaposition with the marking particle developed image-wise charge pattern on the dielectric member. A suitable electric field is applied to transfer the marking particles to the receiver member in the image-wise pattern to form the desired print image on the receiver or intermediate transfer member. In the case of an intermediate transfer member, a secondary transfer step is performed whereby a second suitable electric field is applied to transfer the marking particles from the intermediate receiver member to the receiver member. The receiver member is then removed from its operative association with the dielectric member and the marking particle print image is permanently fixed to the receiver member typically using heat, and/or pressure. Multiple layers or marking materials can be overlaid on one receiver, for example layers of different color particles can be overlaid on one receiver member to form a multi-color print image on the receiver member after fixing.
In the earlier days of electrographic printing, the marking particles were relatively large (e.g., on the order of 10-15 μm). As a result the print image had a tendency to exhibit a relief (variably raised surface) appearance. Under most circumstances, the relief appearance was considered an objectionable artifact in the print image. In order to improve image quality, and to reduce relief appearance, over the years, smaller marking particles (e.g., on the order of less than 8 μm) have been formulated and are more commonly used today.